Low-Valent Group 14 Species Supported by BICAAC: Isolation of a Germylone and a Digermanium Compound

Herein, we have disclosed the successful isolation and spectroscopic characterization of a series of bicyclic (alkyl)(amino) carbene (^Me/iPrBICAAC) complexes of GeCl₂ and SnX₂; [^MeBICAAC-GeCl₂ (1); ^iPrBICAAC-GeCl₂ (2); ^MeBICAAC-SnX₂ (X = Cl (3); X = Br, (4))]. The in-situ KC₈ reduction of GeCl₂·dioxane in the presence of ^MeBICAAC led to the isolation of a zero-valent di-coordinated germylone [(^MeBICAAC)₂Ge] (5), whereas the reduction of adduct 2 afforded a trans-bent digermanium complex, [^iPrBICAAC→Ge═Ge←^iPrBICAAC] (6), having a Ge═Ge (2.3652(5) Å) double bond. Additionally, complexes 3 and 4 were reacted with diironnonacarbonyl Fe₂(CO)₉ to produce the corresponding Sn→Fe adducts 7 and 8, respectively. Further, attempts were made to convert the ^MeBICAAC-Sn adducts 3 and 4 to the corresponding tin-hydride complex, by treatment with LiBH₄, however, in both the attempts, uncontrolled hydrogenation occurred to give the dihydrogented ^MeBICAAC complex, ^MeBICAAC(H₂) (9). The solid-state structures of compounds 1-8 have also been elucidated using single-crystal X-ray diffraction technique. Further, computational investigations were performed to explain the bonding situation in 3-8 that establishes the ylidone character of 5, and supports the formation of 7-8 via donation of the lone pair at Sn to the Fe center.